The flow behaviour of pigments based on flake-form substrates, such as, for example, mica flakes, is frequently unsatisfactory. In a multiplicity of applications, in particular in the printing and paints sector, this does not result in major problems. On incorporation into plastics, however, the poor flow behaviour of these pigments proves to be particularly problematic.
In addition, pronounced evolution of dust occurs during the processing of pearlescent pigments, for example in the preparation of masterbatches, which requires increased equipment complexity for elimination of the dusts and for cleaning of the machines.
It is known per se to coat pigments with organic components in order to simplify incorporation of the pigments, for example into plastics, powder coatings, toners, etc. Processes of this type for the preparation of pigment compositions and pigment-containing granules are known, for example, from DE 26 03 211, WO 2005/052076, WO 2005/019327 and U.S. 2002/0098435 A1.
The mechanical properties of effect pigments based on flake-form substrates are frequently very unsatisfactory, which is evident in the form of dusty abraded material owing to fracture of the pigments and loss of adhesion of the coating from the support substrate in the form of delamination. A further problem is the increase in throughput in the extrusion process on incorporation of pigment-containing compositions into plastics. The compositions from the prior art are frequently distinguished by inadequate oxidation stability.
Furthermore, however, it has been found that the pigment granules known from the prior art comprising >50% of effect pigments and an organic polymer are frequently not oxidation-stable and tend towards dangerous spontaneous heating, although pigment granules of this type should not be classified as readily combustible solids (in accordance with test procedure A.10. Combustibility of Solid Substances in the Official Journal of the European Communities No. L 383 A/76 of Dec. 29, 1992).